Fast asleep:

睡得很快 ×

酣睡 √

例句：

They were both fast asleep in their cots.

他們倆在嬰兒床上酣睡著。

In the pink:

穿粉色的 ×

身體健康 √

例句：

A glass of red wine keeps you in the pink.

一杯紅酒有益健康。

In the swim:

在里面游泳 ×

跟上形勢(shì) √

例句：

As a police officer, I have to stay in the swim of what's going on in the streets and in our neighborhoods. 

作為警官，我必須十分了解街上和我們街區(qū)里發(fā)生的事情。